The idea was to have a veteran backup who knew the NFL and knew his team’s offense so well that he could step in and play without getting antsy.

A backup quarterback had to be somewhat heroic. If he was forced into action on a given Sunday, you wanted him to step in and come out throwing.

He needed to be good enough to put the opposing defense on its heels.

Then after the initial blush, he needed to be good enough to step in and lead a team for weeks at a time.

The greatest backup quarterback performance came in 1972. That was the season the Miami Dolphins ran the table, going 14-0-0 in the regular season and three more games in the postseason to become the only undefeated, championship team of the modern era.

Don Shula had a brilliant defense and a very strong running game. Starting quarterback Bob Griese was more than a caretaker, but he was not asked to throw for 300 yards and three touchdowns every game. His job was to hand the ball off to Larry Csonka, Jim Kiick or Mercury Morris and throw the occasional pass to speedy Paul Warfield. (If you don’t remember Warfield, think Reggie Wayne. They were quite comparable.)

But Griese did not last long in that undefeated season. Shula had to turn the quarterback position over to 38-year-old Earl Morrall early in the season when Griese suffered a broken leg and dislocated ankle.

Morrall was a tobacco-chewing, non-showering character who knew more than most coaches about playing quarterback. He had a calming impact on his Dolphin teammates –despite his malodorous ways – along with an accurate delivery and a quick release.

He went 9-0-0 as the Dolphins starter and completed 55.3 percent of his passes along with 11 touchdowns and seven interceptions.

Morrall had started 92 games in his career before than ’72 season and he was not surprised by anything he saw from opposing defenses. That experience is why Shula plucked Morrall from the waiver wire before the ’72 season.

There are no Earl Morrall-types any more. The salary cap makes finding a backup quarterback of that ilk almost impossible.

Experience is still a vital factor, and that’s why Bears backup Jason Campbell rates fairly high. He has started 70 games in his career. However, accurate passing is the best factor in finding a backup quarterback, followed closely by quick release.

Here’s a quick look at the top eight backup quarterbacks in the league.

1. T. J. Yates, Houston – Yates earned this status after he filled in for injured Matt Schaub. Not only did he lead them down the stretch in the regular season, he was in the lineup for a playoff victory. Head coach Gary Kubiak like his calm demeanor as well as his accuracy on short- and medium-range passes.

2. Matt Flynn, Seattle – Flynn has only started two games, but he has perhaps the strongest arm of any backup and that gives him an advantage. Many expected Flynn to be the starter with the Seahawks this year, but he could not beat out athletic Russell Wilson. Flynn has excellent understanding of the position and he is accurate.

3. Jason Campbell, Chicago – The Bears fell apart last year when Jay Cutler went down and they were unprepared at the backup position. Campbell has 70 starts in his career and he should not be surprised by anything he sees. He does not have the strongest arm but he gets rid of the ball quickly.

4. Ryan Mallett, New England – It would seem that the Patriots are making a huge gamble because they don’t have an experienced backup behind Tom Brady. Mallett has never started a game, but Bill Belichick believes he has all the tools and that he would be able to handle the job if Brady was unable to go.

5. Byron Leftwich, Pittsburgh – You don’t have to be a pro football scout to see Leftwich’s flaws. He is a big man who lacks overall athleticism and has a huge wind-up. Leftwich has a strong arm and can put the ball on the money once he’s comfortable in the pocket. He has started 49 games and the Steelers are hoping he’s quick enough to handle the Baltimore pass rush this weekend as he takes over for Ben Roethlisberger (ribs).

6. Matt Moore, Miami – Ryan Tannehill has certainly been a positive as a rookie quarterback, but Moore has shown he can throw the ball competently. He moves around the pocket very well and has some zip on his passes. He completed 60.5 percent of his passes while starting 12 games for the Dolphins last year and he has 25 starts in his career.

7. Drew Stanton, Indianapolis – He does not compare well to Andrew Luck in terms of arm strength or quick release, but Stanton is smart and athletic. He can move around the pocket and buy time and he is fairly accurate. Stanton has not played since the 2010 season with the Lions.

8. David Carr, N.Y. Giants – Based on experience, Carr should be at the top of this list. He has started 79 games in his career. He has a powerful arm and great size, but he has not started a game since ’07.

Steve Silverman

Steve Silverman is an award-winning writer, covering sports since 1980. Silverman was with Pro Football Weekly for 10 years and his byline has appeared in the Wall Street Journal, Playboy, NFL.com and The Sporting News. He is the author of four books, including Who’s Better, Who’s Best in Football — The Top 60 Players of All-Time. Follow him on Twitter (@profootballboy) and read more of his CBS Chicago columns here.